For a great many years flushing toilets, pans and bowls have been in existence, and the water closet in one form or another, is common place in all modem homes. With the conventional low flush or close coupled toilet cistern and pan, the means for achieving the flush consists either of a siphon (which at present for the U. K. is still the only acceptable device that meets the water byelaws) or one of a number of non-siphon type valves used extensively on the continent and elsewhere in the world.
These non-siphon on direct type valves, have a valve plate or member which covers and seals the outlet to prevent water from escaping unintentionally. Both the siphon and the direct type flush valve have a threaded outlet pipe which extends downwards through the bottom of the cistern into which it is fixed by a bulkhead fitting. It is then connected to the toilet pan either directly or by a short length of pipe.
With the sole means of flushing or cleaning the pan being the water discharge from the cistern 1 the effectiveness of the flush is mainly dependent on flow rate. Most siphons do not have a good flow rate and require a considerable amount of water to achieve a satisfactory flush; moreover they are sensitive to changes in water level setting and most do not perform satisfactorily below a medium level setting. With some-siphon installations, the flow rates are so low that in some cases more than one flush-is necessary.
Non-siphon type valves generally achieve greater flow rates and with the kinetic energy of the water in the pan approximately doubling for a 50% increase in flow rate, less water is required for an effective flush. In fact the performance of most U. K. toilet pans could be considerably improved by replacing the siphon with a direct discharge valve. Some existing installations in the U. K. and elsewhere would accommodate even higher flow rates than are generally available with existing flush valves. For new installations, by designing the galleries and contours of the pan and cistern in conjunction with a high performance non-siphon flush valve, the quantity of water required for effective flushing could be substantially reduced. For instance with a valve of the type described in this specification installed in the U. K. the amount of water required could be reduced from 7 liters to 3.5-4.5 liters full flush capacity for all installations since January 1993 and from 9 liters to 3.5-4.5 liters for installations prior to then. Moreover when the valve is operated in its short flush mode only 1.5-2.0 liters are required.
In my patent GB-B-2274344 I have described a discharge valve of improved performance and the present invention aims to provide further improvements in this respect.
Accordingly it is an object of the present invention to provide a fluid outlet valve to increase and enhance the performance of water closets.
It is a further object to provide a valve that can operate a full or partial flush, a so-called dual flush valve.
It is also an object to provide a convenient overflow means through the valve, with the added advantage of the quantity of water required for fully or partly flushing being considerably reduced.